Method and system for charging electric vehicles

ABSTRACT

An electric vehicle charger determines the presence of an electric vehicle when the electric vehicle is in proximity to the charger. Validation of account data associated with the electric vehicle occurs over a network. A docking interface on the charger aligns to a receptacle on the electric vehicle. The docking interface and the receptacle are coupled when the docking interface is within a predetermined distance to the receptacle. The charger supplies power to the electric vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a utility application claiming priority to U.S. Provisional Application Ser. No. 61/246,524 filed on Sep. 28, 2009 entitled “ROBOTIC ELECTRIC VEHICLE CHARGING SYSTEM,” the entirety of which is incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates generally to electric powered vehicles. More specifically, the invention relates to an autonomous charging infrastructure to alleviate the task of charging electric vehicles.

BACKGROUND

Electrically powered vehicles (EV) and battery electric vehicles (BEV) have numerous advantages over fossil fuel cars including reduced emission of pollutants and national dependency on foreign energy sources. Despite these advantages, EVs suffer from short driving range and long charging intervals due largely to battery technology limitations. Accordingly, both widespread adoption of EVs and a charging infrastructure has been limited. Hybrid electric vehicles (HEV) or plug-in hybrid electric vehicles (PHEV) attempt to mitigate the range and charging interval issues by providing an alternate power source, for example fossil fuel or hydrogen.

Typical electric charging stations require the vehicle user to manual connect the car to the station. With the required frequency of charging such manual intervention complicates vehicle ownership and thus vehicle adoption.

Another approach uses near field magnetic resonance induction. This approach suffers from electromagnetic interface and lower coupling efficiency between the power source and the vehicle.

To fully realize the potential of EVs and encourage their adoption, charging should occur with limited or no user intervention as an unconscious task. This requires an intelligent system to transfer power between a variety of power sources and the vehicle. In addition, there needs to be a way to appropriately bill for this service regardless of who is driving the vehicle as would occur with a rental fleet.

BRIEF SUMMARY

In one aspect, the invention features a method for charging an electric vehicle. The presence of an electric vehicle proximate to a charger is determined. The user account data associated with the electric vehicle is validated. A docking interface on the charger is aligned to a receptacle on the electric vehicle. The docking interface is coupled to the receptacle when a proximity is less than a predetermined distance. Power is supplied from the charger to the electric vehicle.

In another aspect, the invention features a system for charging an electric vehicle. A robotic arm is configured for coupling to an electric power source. A docking interface is coupled to the robotic arm. An imager is coupled to the docking interface and is in communication with a plurality of electrical connectors disposed in the docking interface. At least one of the electrical connectors is configured for electrical communication with the electric power source.

In another aspect, the invention features a system for charging an electric vehicle. A behaviors module comprises a usage database to store data indicating a charging behavior of an electric vehicle. A charging apparatus has a power switch and is configured for communication with the behaviors module through a communications network. The charging apparatus is configured to electrically couple the electric vehicle and a power grid through the switch in response to a request from an electric power source on the power grid.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The above and further advantages of this invention may be better understood by referring to the following description in conjunction with the accompanying drawings, in which like numerals indicate like structural elements and features in various figures. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

FIG. 1 is a perspective view of an embodiment of a system for charging electric vehicles according to the invention.

FIG. 2 is a perspective view of an electric vehicle and a charger illustrated in FIG. 1.

FIG. 3A is a perspective view of an embodiment of a docking interface.

FIG. 3B is a perspective view of an embodiment of a receptacle usable with the docking interface in FIG. 3A.

FIG. 3C is a cross-sectional view of FIG. 3A taken along A-A′, further illustrating a spring-loaded imager and an electromagnet.

FIG. 4A is a perspective view of an embodiment of a docking interface.

FIG. 4B is a perspective view of an embodiment of a receptacle usable with the docking interface in FIG. 4A.

FIG. 4C is a cross-sectional view of FIG. 4A taken along B-B′, further illustrating the spring-loaded imager.

FIG. 5 is a perspective view of the embodiment of the docking interface in FIG. 4A modified to move the imager.

FIG. 6 is a perspective view of the embodiment of the docking interface in FIG. 4A in relation to three axis defining the six degrees of freedom.

FIGS. 7A, 7B and 7C illustrate coaxial alignment using features on a receptacle.

FIGS. 8A and 8B illustrate the proximity of a receptacle in the field of view.

FIGS. 9A and 9B illustrate the roll alignment using features on a receptacle.

FIGS. 10A and 10B illustrate the pitch alignment of a receptacle in the field of view.

FIGS. 10C and 10D illustrate the yaw alignment of a receptacle in the field of view.

FIG. 10E illustrates a receptacle with coaxial misalignment, roll misalignment, pitch misalignment and yaw misalignment.

FIG. 11 is a schematic view of an embodiment of a mesh network according to the invention.

FIG. 12 is a schematic view of an embodiment of a metering architecture according to the invention.

FIG. 13A is a schematic view of the mesh network in FIG. 11 showing a communication path.

FIG. 13B is a schematic view of the mesh network in FIG. 13A showing a repaired communication path.

DETAILED DESCRIPTION

Embodiments of charging methods and systems described herein provide for intelligent power management between a power grid and an electric vehicle (EV) including combinations of vehicle charging and use of the vehicle to return power to the grid. The embodiments described herein refer to EV. An EV can include a battery electric vehicle (BEV), hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV) and any transportable device that generates or consumes electricity and benefits from autonomous charging. For example, an EV can be a golf-cart, a fork-lift or an electric shopping-cart. Autonomous means that the act of charging the EV or sharing the EV power with the power grid occurs with little or no user action. In so doing, the limitations of frequent and long charging intervals associated with EVs, relative to fossil fuel vehicles disappears thereby facilitating the widespread adoption of EVs.

In one embodiment a user parks an EV at a work site and leaves the EV. In another embodiment the EV is parked at home and the user goes to sleep. A robotic charger detects the presence of the vehicle. Account data associated with the EV either contained in a key, on a receptacle on the EV or both are transmitted wirelessly to a resource that validates whether the grid should charge the car, whether the car should charge the grid and manages billing information. The charger connects to the EV using machine vision and charging proceeds until the user returns to the car, a full charge occurs or some other event terminates the charging process. At this time the charger undocks and stows away awaiting the next EV.

FIG. 1 illustrates an embodiment of a charging system 10 for four EVs 12 a, 12 b, 12 c and 12 d (generally 12) each having a corresponding receptacle 18 a, 18 b, 18 c and 18 d (generally 18) respectively. In one embodiment each EV 12 has more than one receptacle to facilitate coupling to the charger. Each EV 12 is shown at various stages of docking with chargers 14 a, 14 b, 14 c and 14 d (generally 14). Each charger 14 has a corresponding docking interface 16 a, 16 b, 16 c and 16 d (generally 16) used to couple with the corresponding receptacle 18 on the EV 12.

Each EV 12 and each charger 14 communicates wirelessly with a coordinator 30. The coordinator 30 communicates through an Internet 34 by way of an Internet gateway 32. The Internet connects to a plurality of resources including computers 36 a and 36 b (generally 36). The Internet 34 may also be a cloud-computing environment where a large number of resources, for example computers, are in communication with the Internet gateway 32. The Internet gateway 32 is preferably a ruggedized tablet personal computer (PC) but may also be any computing device capable of passing low data rate files between the coordinator 30 and the Internet 34.

The wireless communication preferably uses the Institute of Electrical and Electronic Engineers (IEEE) 802.15.4 standard (Zigbee™). Zigbee™ is optimal for control and sensor networks that have low data rate, low power consumption and small packet sizes. Other wireless protocols may be used in place of, or in combination with, Zigbee™ including but not limited to MiWi™, ANT™, IEEE 802.15.1 (Bluetooth®), IEEE 802.11 (WiFi™), IEEE 802.16 (WiMax™), and Long Term Evolution (LTE™).

Each charger 14 also communicates with a power grid 20, which connects to numerous electric power sources, for example a wind turbine 22, a coal burning power plant 24 or an array of solar cells 26. Preferably the chargers 14 support either Level-1 (e.g. single phase 120V), Level-2 (e.g. single phase 230/240V) or any Level-3 (e.g. three phase) power standard, although the chargers 14 are envisioned to be usable with any power line standard available including different frequencies such as 50 Hz and 60 Hz.

The charging system 10 of FIG. 1 illustrates the various stages of docking or coupling a receptacle 18 on an EV 12 with a docking interface 16 on a charger 14. EV 12 a has just arrived at a parking spot. Charger 14 a senses the proximity of EV 12 a when a wireless signal transmitted from EV 12 a is strong enough to be detected by charger 14 a and determined to be of sufficient magnitude. The charger 14 a also ensures that the EV 12 a is stationary before attempting to dock. Charger 14 a may also use auto-ranging techniques including sonar or measuring the acoustic delay of a signal transmitted by the charger 14 a, reflected by the EV 12 a and returned to the charger 14 a. In other embodiments the auto-ranging may measure the delay of a light beam or sense the magnetic field distortion when a magnetic field emitted by the charger 14 a is proximate to metal contained in the EV 12 a.

In addition to sensing proximity of the EV 12 a to the charger 14 a, the roll angle of the EV 12 a is transmitted to the charger 14 a to facilitate subsequent docking of the docking interface 16 a to the receptacle 18 a. The roll angle of the EV 12 a is measure of how much the EV 12 a leans left or right, for example when the EV 12 a is parked on a sloped surface. The EV 12 a also transmits other charging behavior data, for example the date when the EV 12 a was charged, the time and duration when the EV 12 a was charged and the location where the EV 12 a was charged. The EV 12 a also transmits information for billing purposes such as billing address and account data in a secure encrypted format. In one embodiment, the encryption format is a 128-bit encryption based on the National Institute of Standards and Technology (NIST) Certified Advanced Encryption Standard (AES). Information transmitted by the EV 12 a is received by the coordinator 30 and passed to the Internet gateway 32 for account validation and billing purposes or to determine if the EV 12 a should supply power to the power grid 20 based on the charging behavior of the EV 12 a. For example, if the EV 12 a has excess charge or is expected to remain parked for a long time based on previous charging sessions the EV 12 a could supply power to the power grid 20 when there is high demand for power from other EVs connected to the power grid 20. The account corresponding to the EV 12 a is credited at a favorable billing rate compared to the billing rate used when the EV 12 a previously received power from the power grid 20. In another embodiment the information transmitted by the EV 12 a to the coordinator 30 is used to assess a parking fee for the EV 12 a. In yet another embodiment the EV 12 a can alert the driver of the EV of a potential theft of the EV by sending a signal to the Internet 34 when the EV is moved.

Supplying power from the EV 12 to the power grid 20 is compatible with vehicle to grid (V2G). V2G reduces the demand on power sources 22, 24 and 26 because a large pool of EVs 12 can supplement the power generation of the power sources 22, 24 and 26. The autonomous nature of the charging system 10 improves V2G because an accurate determination of when, where and how to transfer power from an EV 12 to the power grid 20 requires a charging behavior usage database that contains a significant number of charging sessions. This in turn necessitates a system as described with charging system 10 that is easy to use and collects the necessary data for effective V2G without user intervention or manual error.

EV 12 b is at the next stage of docking compared to EV 12 a. The docking interface 16 b on charger 14 b is aligned to the receptacle 18 b on EV 12 b by positioning the docking interface with a robotic arm on the charger 14 b. The robotic arm is capable of articulated movement with six degrees of freedom (sixDOF) and a telescoping arm. Robotic arms with additional degrees of freedom are also envisioned. While preferably a sixDOF robotic arm is used, certain installations may advantageously use a robotic arm with more joints to clear obstacles between the charger 14 b and the EV 12 b.

EV 12 c is at the next stage of docking compared to EV 12 b. After the initial alignment stage illustrated with EV 12 b, and when the docking interface 16 c is within close proximity to the receptacle 18 c, the docking interface 16 c is coupled to receptacle 18 c. During the coupling, the alignment of docking interface 18 c to the receptacle 18 c is maintained until coupling is complete. The proximity of docking interface 16 c to the receptacle 18 c is sufficiently close when less than a predetermined distance that is defined by a value stored in the charger 14 c.

Determining the proximity of the docking interface 16 c to the receptacle 18 c is based on methods similar to the initial determination that EV 12 a was sufficiently close to charger 14 a. Specifically, the charger 14 c may use auto-ranging techniques including sonar or measuring the acoustic delay of a signal transmitted by the charger 14 c, reflected by the EV 12 c and returned to the charger 14 c. In other embodiments the auto-ranging may measure the delay of a light beam or sense the magnetic field distortion when a magnetic field emitted by charger 14 c is proximate to metal contained in EV 12 c.

In one embodiment, coupling of the receptacle 18 c with the docking interface 16 c includes achieving a physical connection between electrodes on the receptacle 18 c and electrodes on the docking interface 16 c. In another embodiment, the receptacle 18 c couples to the docking interface 16 c with a magnetic field with power transferred through near-field inductive coupling. In yet another embodiment, the receptacle 18 c couples to the docking interface 16 c with an optocoupler. Once the receptacle 18 c is coupled to the docking interface 16 c, the charger 14 c performs supplies power from the power grid 20 to the EV 12 c, supplies power from the EV 12 c to the power grid 20, or both. In one embodiment, the charger 14 c contains a current limit device to lower the charging rate with a corresponding reduction in billing charges.

EV 12 d is at the next stage of docking compared to EV 12 c. The EV 12 d is charged by charger 14 d. The EV 12 d signals the end of a charging session expressly or as a fail-safe when the EV 12 d begins to move. The charger 14 d then stores the robotic arm as depicted with charger 14 a.

In addition to charging the EV 12 or returning power to the power grid 20 with V2G, the charging system 10 also enables a user to control a device of the EV 12 by sending a control signal through the Internet 34 to the coordinator 30 to be communicated to the EV 12. In one embodiment the control signal received by the EV 12 controls the EV 12 air conditioning, heating and lighting systems by further communicating with the EV 12 controller area network (CAN) or local interconnect network (LIN) bus. A CAN or LIN bus provides communication between a variety of devices in an EV such as heating systems, lighting and radios. The control signal received by the EV 12 is beneficial to start a car to warm the cabin before a driver arrives or to activate lights to locate a car in a crowded lot for example.

FIG. 2 further illustrates the docking interface 16 b on charger 14 b aligning to the receptacle 18 b on EV 12 b as shown in FIG. 1. In one embodiment the receptacle 18 b is on the front of the EV 12 b. In other embodiments, the receptacle 18 b is on the rear or on the side of the EV 12 b. In yet another embodiment, multiple receptacles are available for the charger 14 b to choose from based on proximity.

FIG. 3A shows an embodiment of a docking interface 52 with a plurality of electrical connectors 56, an electromagnetic surface 60 and an imager 64. The surface 60 is magnetized by an electromagnet that is powered by the charger 14 when docking the charger 14 to the EV 12. After charging is complete, the electromagnet is deactivated thereby facilitating the undocking of the charger 14 to the EV 12. The electrical connectors 56 include a combination of power, ground and signals. In one embodiment the imager 64 is responsive to infrared light and contains a field of view sufficient to see the receptacle 16 during docking as illustrated in FIG. 1.

FIG. 3B shows an embodiment of a receptacle 54 with a plurality of electrical receptors 58, a magnetized surface 62, a west feature 66, a north feature 68, an east feature 70 and a centroid feature 72 mounted on a pedestal 74. In one embodiment the length of the pedestal 74 is approximately the same as the distance between the west feature 66 and the east feature 70, which is 74 mm in one instance. The docking interface 52 shown in FIG. 3A is a female connector and the receptacle 54 shown in FIG. 3B is a male connector. It is contemplated that the docking interface 52 may be a male connector and the receptacle 54 a female connector, or the docking interface 52 may be a female connector and the receptacle 54 a male connector. The electrical connectors 56 and the electrical receptors 58 are designed to couple with a friction fit however they may also be capacitively coupled or inductively coupled to further isolate the EV 12 from high voltages for safety reasons. In one alternative embodiment the surface 62 on the receptacle 54 is an unmagnetized metallic surface. In another embodiment the surface 62 is an electromagnet powered by the EV 12 when docking the charger 14 to the EV 12 and the surface 60 on the docking interface 52 is either metallic, a permanent magnet or an electromagnet.

Features 66, 68, 70 and 72 may be reflective emblems illuminated by a light source in the docking interface 52, or may be light emitting diodes (LEDs) or a light pipe formed by a fiber optic thread illuminated by a light source. In one embodiment the LEDs are preferably infrared LEDs with a 7.5 Hz square-wave amplitude modulation. The LED frequency and modulation scheme is preferably chosen to be responsive to emissions from the receptacle features and not responsive to ambient light or heat sources that may interfere with the receptacle emissions. In another embodiment additional features are present to provide redundancy in case a feature is obscured or to achieve increased accuracy.

In one embodiment, the imager 64 of the docking interface 52 has a wiper mechanism to keep the imager 64 free of dirt and snow. Alternatively, the imager 64 of the docking interface 52 has an iris shutter to keep the imager 64 free of dirt and snow. In another embodiment, the imager 64 of the docking interface 52 has forced hot air blown across it through one of the electrical connectors 56. A heater and blower on the charger 14 provides a flow of heated air through a tube from the charger 14 to one of the connectors 56. In another embodiment, the imager 64 is heated with a thermostatic heater. Specifically, the spring 76 in FIG. 3C is heated and heat is conductively transferred to the imager 64.

FIG. 3C shows the cross-section of FIG. 3A taken along A-A′ and illustrates the electrical connector 56 with a friction fit adapted to receive an electrical receptor 58 on the receptacle 54. The imager 64 is spring-loaded by a spring 76 and communicates with the charger 14 of FIG. 1 with signals 78. The spring 76 is a low compression force spring allowing the pedestal 74 of receptacle 54 to compress the spring 76 during the docking process. Docking interface 52 has an electromagnetic surface 60. The polarization of the surface 60 can be removed or reversed after charging of the EV 12 or transferring power to the power grid 20 is complete.

FIG. 4A shows a modification of the embodiment of the docking interface 82 shown in FIG. 3A, where the imager 64 is contained in a threaded hole 88. FIG. 4B shows a modification of the embodiment of the receptacle shown in FIG. 4B where the pedestal contains threads 86 adapted to couple with the threaded hole 88 shown in FIG. 3A.

FIG. 4C shows the cross-section of FIG. 4A taken along B-B′. FIG. 4C is similar to FIG. 3C with the exception that the electromagnetic surface 60 in FIG. 3C is absent. The docking interface shown in cross-section in FIG. 4C uses a threaded screw or auger formed by the threaded pedestal 86 on receptacle 84 to couple to the threaded hole 88 of docking interface 82. In one embodiment, the threaded pedestal 86 is powered by the receptacle 84 to rotate during the docking session and to stop rotating when the docking interface 82 and the receptacle 84 are coupled, determined by conduction between one of the electrical connectors 56 and one of the electrical receptors 58.

FIG. 5 is a modification to the docking interface 82 shown in FIG. 4A where the imager 64 is offset from the centroid feature 72 shown in FIG. 4B. Advantageously, this embodiment does not require the spring 76 shown in FIG. 3C but requires accurate ranging information to establish the distance between the docking interface 82 and receptacle 84 during docking, and the distance between the threaded hold 88 and the imager 64 to compensate for the imager 64 offset during alignment of the docking interface 82 and the receptacle 84.

FIG. 6 shows an embodiment of the docking interface 82 of FIG. 4A in relation to the three axis defining the six degrees of freedom (sixDOF). To properly align the docking interface 82 with the receptacle 84 shown in FIG. 4A and FIG. 4B respectively the docking interface 82 is aligned to the receptacle 84 in six ways. First, the docking interface 82 achieves coaxial alignment by correcting for horizontal misalignment on axis 102 and vertical misalignment on axis 104. Second, the docking interface 82 reduces proximity to the receptacle 84 by moving along axis 106. Third, the docking interface 82 achieves roll 107 alignment. Fourth, the docking interface 82 achieves pitch 108 alignment. Fifth, the docking interface 82 achieves yaw 109 alignment. Each of the sixDOF may be interdependent and require concurrent alignment or each of the sixDOF may be adjusted iteratively.

FIGS. 7A, 7B and 7C illustrate a method of coaxially aligning the docking interface 82 of FIG. 4A to the receptacle 84 of FIG. 4B. In FIG. 7A, the imager 64 shown in FIG. 4A sees four features: the centroid feature 72, the west feature 66, the north feature 68 and the east feature 70. In FIG. 7A, the docking interface 82 is north-west of the receptacle 84 and should be moved to the right and downward to maintain an equal distance between the centroid feature 72 and each of the west feature 66, the north feature 68 and the east feature 70. In FIG. 7B, the docking interface 82 is east of the receptacle 84 and should be moved to the right to maintain an equal distance between the centroid feature 72 and each of the west feature 66, the north feature 68 and the east feature 70. In FIG. 7C, the docking interface 82 has achieved coaxial alignment with the receptacle 84.

FIGS. 8A and 8B illustrate a method of achieving proximity of the docking interface 82 of FIG. 4A to the receptacle 84 of FIG. 4B to within a predetermined distance. In FIG. 8A, the receptacle 84 is far from the docking interface 82 relative to the receptacle 84 shown in FIG. 8B because the distance between the west feature 66 and the east feature 70 is small in comparison to the field of view 126 of the imager 64 shown in FIG. 4A. By increasing the distance between the west feature 66 and the east feature 70, the docking interface 82 is positioned closer to the receptacle 84 as shown in FIG. 8B.

While preferably the west feature 66 and the east feature 70 are used to achieve proximity, maximizing the distance between any two features on the receptacle 84 similarly results in positioning the docking interface 82 closer to the receptacle 84. For example, maximizing the distance between the centroid feature 72 and the west feature 66 ultimately results in moving the docking interface 82 closer to the receptacle 84 even though a concurrently performed coaxial alignment shown in FIGS. 7B and 7C may temporarily interfere with the proximity adjustment, until coaxial alignment is achieved.

FIGS. 9A and 9B illustrate a method of achieving roll alignment of the docking interface 82 of FIG. 4A to the receptacle 84 of FIG. 4B. Specifically, FIG. 9A shows the features on a receptacle 84 rolled about the axis 106 shown in FIG. 6, while FIG. 9B shows the same features on a receptacle 84 after roll alignment is achieved. Preferably an alignment line intersecting the west feature 66 and the east feature 70 is compared with a reference line stored in the charger 14 a of FIG. 1. The reference line stored in the charger 14 a is modified by the roll angle of the EV 12 a to compensate for sloped parking surfaces.

While preferably the west feature 66 and the east feature 70 are used to form the alignment line used for roll alignment, it is contemplated that the alignment line can intersect any two features. Similar to the interaction of concurrently performing coaxial alignment and achieving proximity, the use of the centroid feature 72 and the west feature 66, (or similarly the east feature 70), may cause an interaction between roll alignment and coaxial alignment but ultimately both roll alignment and coaxial alignment are achieved.

FIGS. 10A and 10B illustrate a method of achieving pitch alignment of the docking interface 82 of FIG. 4A to the receptacle 84 of FIG. 4B. FIG. 10A shows the features of the receptacle 84 shifted to the top of the field of view 126 of the imager 64. Pitch alignment is achieved by moving the centroid feature 72 downward to the center of the field of view 126. FIG. 10B shows the features of the receptacle 84 shifted to the bottom of the field of view 126 of the imager 64. Pitch alignment is achieved by moving the centroid feature 72 upward to the center of the field of view 126.

FIGS. 10C and 10D illustrate a method of achieving yaw alignment of the docking interface 82 of FIG. 4A to the receptacle 84 of FIG. 4B. FIG. 10C shows the features of the receptacle 84 shifted to the left of the field of view 126 of the imager 64. Yaw alignment is achieved by moving the centroid feature 72 rightward to the center of the field of view 126. FIG. 10B shows the features of the receptacle 84 shifted to the right of the field of view 126 of the imager 64. Yaw alignment is achieved by moving the centroid feature 72 leftward to the center of the field of view 126.

FIG. 10E shows the features of a receptacle 84 with coaxial misalignment, proximity less than a predetermined distance, roll misalignment, pitch misalignment and yaw misalignment. Each of the sixDOF alignments shown in FIG. 6 can be adjusted concurrently with one or more of the other sixDOF alignments, or each of the sixDOF alignments can be adjusted independently and iteratively. In one embodiment, an initial pitch alignment and a yaw alignment occur first to move the features on the receptacle 84 to the center of the field of view 126. This advantageously improves the accuracy of subsequent alignment steps by using the center of the field of view 126 of the imager 64, where less lens distortion and parallax occurs.

The field of view 126 is designed to cover sufficient area to initially see the features of the receptacle 84. In other embodiments, the imager 64 includes a zoom feature to create a wider field of view 126 to facilitate initial image capture. In another embodiment, the charger 14 of FIG. 1 performs a raster scan movement to facilitate initial image capture. The raster scan movement begins at the top left of the field of travel of the charger 14, moves from left to right, moves downward by less than the height of the field of view 126, scans right to left, moves downward by less than the height of the field of view 126 and repeats the above steps.

FIG. 11 illustrates a mesh network 170 used for simple, scalable and fault tolerant communication between components of a charging system described herein. FIG. 11 shows three EVs 12, each with a smart key 174 and a charger 14. Each charger 14 and each EV 12 is capable of being a wireless router, which means it can retransmit information at the request of other components. Each smart key 174 is a wireless end-point, which means it can respond to a request, but does not retransmit information on behalf of other components, thereby extending the battery life of the smart key 174. A smart key 174 can be a single integrated component or can be a separate module carried on a key chain.

The mesh network 170 includes three chargers 14 acting as charger routers 180, 180 b and 180 c (generally 180), three EVs 12 acting as EV routers 176 a, 176 b and 176 c (generally 176) and three smart keys 174 acting as smart key endpoints 172 a, 172 b and 172 c (generally 172). Each charger router 180 can retransmit data from any other charger router 180, any other EV router 176 and the coordinator 30. Each EV router 176 can retransmit data from any other EV router 176, any charger router 180, any smart key endpoint 172 and the coordinator 30. Each smart key endpoint 172 cannot retransmit data but can respond to a request from any EV router 176 or the coordinator 30. For readability, the coordinator 30 in FIGS. 11, 12, 13A and 13B is shown communicating with only one charger router 180 c, one EV router 176 c and one smart key endpoint 172 c however the coordinator 30 communicates directly with all charger routers 180, all EV routers 176 and all smart key endpoints 172.

Communication between each of the routers and endpoints in the mesh network 170 occurs in a daisy-chained fashion. For example the smart key endpoint 172 a can communicate with the charger 180 a through the EV router 176 a or though the EV router 176 b. The mesh network 170 is tolerant of high latencies and low data rates between routers and endpoints. The inherent redundancy of the mesh provides for fault tolerant operation and scalability. Additional chargers 14 can easily be added or chargers 14 taken down for maintenance without adversely affecting the other chargers 14.

In one embodiment each EV router 176 is a single receptacle 18 on the EV 12. Accordingly, the receptacle 18 on the front of an EV 12 can be coupled to a charger 14 but a second receptacle on rear or side of the EV 12 can retransmit data from the charger router 180 or the smart key endpoint 172.

The smart key 174 and the smart key endpoint 172 contain data associated with an account holder, typically the driver. The EV 12 or a receptacle 18 thereon contains data associated with the EV 12. The separation of data associated with the account holder and the EV 12 provides for a shared car experience where a parent and a teenage driver can each use the same car with separate keys for billing purposes or to store preferences such as charging behavior. An account holder can also use the smart key 172 in a rental car scenario or a borrowed car scenario for billing and personalization.

When the EV is parked and ready to be charged, the smart key 174 pairs with and activates a receptacle 18 to enable charging. The smart key 174 can then be removed during charging. In one embodiment, the smart key 174 is also the ignition key and automatically enables charging by detecting when the ignition key has been removed from the EV 12. Upon returning to the car, the driver inserts the ignition key and the smart key 174 is updated with charging information from the charger 14 used to charge the EV 12.

Each of the charger routers 180 monitors the signal strength of other charger routers 180 and EV routers 176, and each of the EV routers 176 monitors the signal strength of other charger routers 180, EV routers 176 and smart key endpoints 172, and transmits the signal strength information to the coordinator 30 directly or through a daisy chained path in the mesh. The coordinator 30 uses the signal strength information to create a routing map of possible communication paths between any of the elements in the mesh. The coordinator 30 also communicates through the Internet 34 with resources including computers 36 a and 36 b through the Internet gateway 32. In one embodiment, the Internet gateway is a computer configured as a file server. The routing map can be a real time response or it can be stored in a database in communication with the coordinator 30. For example, the routing map can be stored on a computer 36 a or 36 b. Each of the charger routers 180, EV routers 176 and smart key endpoints 172 becomes aware of the possible communication paths by receiving a beacon from the coordinator 30. The beacon is a packet of data containing the communication paths for each element in the mesh network 170.

FIG. 12 shows the mesh network 170 of FIG. 11 further including a metering architecture and additional Internet resources. The charging system 10 of FIG. 1 is designed to easily work with an existing power grid 20 infrastructure. Each charger router 180 communicates with a physical power meter 196 and with a physical legacy meter 198. The legacy meter 198 measures all power supplied to or from the power grid 20. Each power meter 196 measures all power supplied to or from the charger 14 including multiple charging sessions with multiple EVs 12.

In one embodiment, upon completion of a charging session with an EV 12 a virtual power meter 200 in communication with the coordinator 30 records the power consumption of the power meter 196, which is transmitted by the charger router 180 and associates the power consumption with the particular EV 12 receiving or supplying power. The coordinator 30 then transmits the power consumed to a virtual meter 194 associated with an EV 12 and to a virtual meter 192 associated with an account holder. The virtual meters 192, 194 and 200 appear as physical meters to the mesh network 190 but store data representing power supplied or power consumed in non-volatile storage. In one example, the non-volatile memory is Flash memory.

The physical meters 196 are read with automatic meter reading (AMR), which is a wireless protocol to transfer the power meter data to the charger router 180. The coordinator 30 monitors and records the aggregate power consumption or transfer from information sent by the power meters 196 to determine the amount of power consumed or transferred to the power grid 20 exclusive of regular premise use outside of the charging system 10, for example an industrial plant 201.

Data collected from each charging session is stored in a behaviors module 204. In one embodiment the behaviors module 204 stores at least one of the date, time and duration when the EV 12 was charged and the location where the EV 12 was charged. The collected data are useful for V2G to determine which EVs 12 can advantageously return power to the power grid 20. The collected data can also facilitate targeted marketing to vehicle owners. In one embodiment, the coordinator 30 uses an arbiter 206 to determine which EV 12 should supply power to the power grid 20 and how it should do so. For example, one EV 12 may provide sufficient power for V2G; however, several EVs 12 can be available to supply the necessary power. In one example, the arbiter chooses an EV 12 that is most likely to remain coupled to the charger 14 during an entire charging session based on past charging behavior recorded in the behaviors module 204.

The coordinator 30 also communicates with a validation module 202, which stores account information required to authorize a charging session. The validation module can also store parking infractions or other data that could prevent the EV 12 from using the charging services.

The validation module 202, behaviors module 204 and the arbiter 206 can each include a single database containing data for all EVs 12 using the charging system 10 or can include multiple databases, for example a database for each EV 12.

FIG. 13A illustrates an example of a communication path as described in FIG. 11. In one embodiment, each of the smart key endpoints 172, EV routers 176 and charger routers 180 receives a beacon from the coordinator 30 defining either preferred or available communication paths. The smart key endpoint 172 a and the EV router 176 a communicate through a wireless path 212. The EV router 176 a and the charger router 180 a communicate through a wireless path 214. The charger router 180 a and the charger router 180 b communicate through a wireless path 216. The charger router 180 b and the charger router 180 c communicate through a wireless path 218 and the charger router 180 c and the coordinator 30 communicate through a wireless path 220. In another embodiment, any of the smart key endpoint 172 a, the EV router 176 a or any of the charger routers 180 communicates directly with the coordinator 30.

FIG. 13B shows the routing mesh network 210 of FIG. 13A to further illustrate how the communication paths are managed. In FIG. 13B the charger router 180 b has failed, thereby breaking the daisy chained path used in FIG. 13A. The coordinator receives signal strength information from as least one of charger routers 180 a and 180 c one of EV routers 176 a, 176 b or 176 c. In one embodiment, the coordinator 30 determines that the next best path from the smart key endpoint 172 a to the coordinator 30 based on the loss of signal from charger router 180 b and sends a new beacon to all elements in the mesh network 210. The daisy-chained path is then modified to use EV router 176 b instead of charger router 180 b to complete the path. Accordingly, charger router 180 a and EV router 176 b communicate through a wireless path 232, and EV router 176 b and charger router 180 c communicate through a wireless path 234.

Although wireless communication has been described throughout the embodiments and in further detail in FIG. 1, other communication paths are contemplated. For example, one or more wireless path could instead use optical links or other spectral emissions of any frequency. Certain links could also be implemented with wired connections, for example path 220 between the charger router 180 c and the coordinator 30.

While the invention has been shown and described with reference to specific preferred embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the following claims. 

What is claimed is:
 1. A system for charging an electric vehicle comprising: a robotic arm configured for coupling to an electric power source; a docking interface coupled to the robotic arm; an imager coupled to the docking interface and in communication with a controller configured to control a position of the robotic arm; and a plurality of electrical connectors disposed in the docking interface, at least one of the electrical connectors configured for electrical communication with the electric power source wherein the docking interface is configured to couple to a receptacle on an electric vehicle, the receptacle including a plurality of features for detection by the imager and a plurality of electrical receptors, each electrical receptor configured to electrically couple to a respective one of the electrical connectors in the docking interface.
 2. The system of claim 1 further comprising an engagement mechanism to secure the docking interface to the receptacle.
 3. The system of claim 1 wherein the plurality of features includes a west feature, a north feature, and an east feature each disposed in a spherical arc concentric to a centroid feature, the west feature, the east feature and the centroid feature collinear with each other, and the north feature equidistant from the west feature and the east feature.
 4. The system of claim 1 further comprising a coordinator in communication with a plurality of chargers through a network, the coordinator determining a plurality of communication paths from one of the chargers to the coordinator, each of the chargers configured to retransmit a beacon from one of the coordinator, one of the other chargers or a receptacle of an electric vehicle through at least one of the communication paths, and the receptacle configured to retransmit the beacon from one of the coordinator, the chargers or another receptacle through at least one of the communication paths.
 5. The system of claim 1 wherein the receptacle further comprises a virtual meter for storing charging event data in a memory device of the electric vehicle, the virtual meter accessible for determining a charging behavior of the electric vehicle based on the charging event data. 